STUDIES ON LIFE-HISTORY OF PROTOZOA. 2OI 



ing with Paramazcium from these cultures, found that alcohol 

 will increase the division-rate above the control, by about 33 per 

 cent. Under the action of the alcohol the organisms are always 

 lively and appear transparent as though all food were rapidly di- 

 gested. The result is interpreted as a stimulus to the digestive 

 processes effected by the alcohol. 1 In the period of depression 

 which is represented by the 62Oth generation, alcohol brought 

 about no stimulus and the organisms died as rapidly as the ones 

 not thus treated. 



As the age of the race increases, it is conceivable that some- 

 thing in the chemical make-up of the protoplasm becomes de- 

 pleted, something which cannot be replaced from the constituents 

 of the ordinary food medium. With the change of diet, however, 

 new substances are introduced into the protoplasm and renewed 

 activity results. Thus with the change from hay-infusion to 

 beef-extract, chemical substances are introduced into the proto- 

 plasm which could not be obtained from the hay-infusion. In 

 the New York water there are certain chlorides, nitrates, etc., all 

 in extremely minute quantities and these are present of course in 

 the hay-infusion. They are also present in the beef-extract 

 which is made with the same water, but in addition to these salts 

 there are certain extractives from the beef such as potassium 

 phosphate and chloride, lactic acid and lactates, etc., substances 

 of quite a different character from those of the ordinary medium. 

 Added to the fact of a different chemical medium is the fact of a 

 difference in osmotic pressure, for the extract is more dense than 

 the hay-infusion. The extract does not have a direct stimulating 

 effect upon the digestive processes and upon division, for, while 

 the organisms are immersed in it, there is a very slow division 

 rate ; When transferred again to the hay-infusion, however, they 

 divide more rapidly than before. From this it appears that the 

 extract is not a food in the ordinary sense but that it is a stimu- 

 lant acting through the salts dissolved in it. 



These results justify, I believe, the conclusion that, as the po- 

 tential of vitality becomes reduced, something in the chemical 



1 Cf. Calkins and Lieb. Studies on the Life-History of Protozoa. II., The Effect 

 of Stimuli on the Life-Cycle of Paramoccititn caudatum. Arch. f. Protistenk. I., 3, 

 1902. 



